As shown in FIG. 1, an undercarriage typically comprises a leg 1 having a top end hinged to an element of the structure of an aircraft and a bottom end carrying a wheel set 2. In addition, a locking system is provided to hold the assembly securely in the deployed position, as shown in FIG. 1.
The locking system comprises a side brace made up of two hinged-together rods 3 and 4, the rod 3 being hinged to the leg and the other rod 4 being hinged to the structure of the aircraft, with a stabilizer member also being provided for holding the two rods 3 and 4 in alignment with each other.
The stabilizer member comprises two arms 6 and 7 that are hinged together, the arm 6 being hinged for example to the hinge connecting together the rods 3 and 4 while the arm 7 is hinged to the structure of the aircraft. A system of abutments and springs (not shown) holds the arms 6 and 7 in line with each other when the assembly is deployed. Additionally, an unlocking actuator 8 is interposed between the arm 6 and the rod 4 to unlock the entire assembly by retracting the actuator against a spring.
When landing, or while taxiing, the rods 3 and 4, which are held in alignment, are subjected to large forces that can vary suddenly. For example, when the wheels make contact with the ground, they are immediately set into rotation, against their own inertia.
In a known side brace rod structure as shown in FIG. 2, the rod 9 has a tubular portion 11, typically made of aluminum, with two endpieces 12 and 13 fastened to the ends thereof, which endpieces are solid metal parts made by casting or forging, each presenting an opening so as to constitute a respective lug.
The tubular structure for the body of the rod 9 imparts good buckling behavior thereto, whereas the endpieces 12 and 13, given the large amount of material they comprise, provide the required impact strength. Such an endpiece serves to spread the forces that are applied to the pin received in the endpiece in uniform manner to the body of the tubular rod.
In order to reduce the weight of such a rod, it is known to replace the tubular central body of the rod 9 with a tubular central body that is made of composite material, e.g. based on carbon fibers. However, that solution remains limited by the fact that the metal endpieces 12 and 13 are predominant in determining the overall weight of the rod, given the quantity of material they comprise.
In the configuration disclosed in patent document WO 2009/000925, and as shown in FIG. 3, the rod, referenced 14, presents a structure that is generally tubular (ignoring the endpieces) that is constituted by two thin-walled portions 16 and 17 of open or channel section that are engaged one inside the other and adhesively bonded together. Each end of such a rod carries two extensions of the thin wall of one its portions that are shaped to form a pair of lugs or a “clevis” 18 or 19, each lug being made out of an end portion of the thin wall of one of the component portions.
Given the relatively small thickness of the lugs in that rod, the impact strength of those lugs remains well below that required for utilization as a side brace rod.